346 PALAEONTOLOGY OP ILLINOIS. 



. extremity. Since seeing the better specimen alluded to above, we are much 

 inclined to believe this to be the species figured and described by Prof. Hall, 

 under the name Dolabra? alpina, in the Iowa Report (p. 716, pi. 29, fig. 2). 

 It is clearly not a Dolabra, however, but a true Schizodus, as was (in regard to 

 the Iowa specimen) first pointed out by Meek and Hayden, in a note on page 

 58 Palaeontology of the Upper Missouri. 



Both of the casts before us show a rather distinct sulcus, passing obliquely 

 backwards and downwards from the posterior side of each beak along the um- 

 bonal slopes. This sulcus was of course occupied by a corresponding ridge on 

 the inside of each valve. Somewhat similar marks are represented on casts of 

 Schizodus obscurus, figured by Geinitz (Dyas, pi. xiii), though our fossil is very 

 unlike that shell in other respects, and apparently more nearly allied to S. 

 truncatus of King, but still distinct from that also. 



Locality and position: North Branch of Saline creek, Gallatin county, Illinois; 

 Upper Coal Measures. 



Genus EDMONDIA, de Koninck, 1844. 



(Anim. Foss. Oarb. Belg., 66.) 



Edmondia unioniformis, (sp.) Phillips? 



PI. 27, fig. 6, 6a, and 6*. 



Isocardia unioniformis, Phillips, 1836. Geol. Yorks., ii, p. 209, pi. 5, fig. 18. 

 Edmondia unioniformis, de Koninck, 1844. Anim. Foss. Belg., p. 61, pi. 1, figs. 4a, 4b, 4.c . 



Shell gibbous, oval-suborbicular, the length being a little 

 greater than the height; greatest convexity near the middle of 

 the valves; basal margin forming a semi-elliptic or semi-oval 

 curve ; anterior margin rather more narrowly rounded than the 

 posterior, which latter is sometimes faintly truncated; cardinal 

 margin rather short, straight, and horizontal behind the beaks. 

 Beaks gibbous, rather prominent, incurved, and placed a little 

 nearer the anterior than the posterior side. Surface marked 

 with small, irregular, concentric ridges and fine strise, which 

 are apparently sometimes crossed by very obscure traces of 

 radiating lines on the posterior dorsal region. Length, 1.06 

 inch; height, 0.90 inch; convexity, 0.70 inch. 



